Silver
is another unique member of the metals family -the "whitest" of
all metals. In its pure form this moon-colored metal is highly lustrous,
and can be polished to a mirror finish. Silver was known and used by
primitive man. The ancient Hebrews called it by a name meaning pale. The
Greeks knew it by a name meaning shining. American Indians called
it "tears of the moon" The chemical symbol for silver, Ag, comes
from its Latin name, argent.

Like gold, silver is considered a precious metal, and is extremely
malleable and ductile. It is harder than gold, but softer than copper.
Silver can be hammered into sheets so thin that it would take 100,000 of
them to make a stack an inch high. Silver has a specific gravity of 10.5,
and a melting point of 1760ºF (960ºC.)- almost 200ºF below that of
gold.

The
use of the term "sterling" has a historical derivation. In the
12th century, five towns in eastern Germany banded together to form the
Hanseatic League - an entity which engaged in substantial commerce with
England. In payment for English cattle and grain, the League used its own
currency -silver coins called "Easterlings" The English soon
learned that these coins were extremely dependable, and it is believed
that, under the reign of Henry II, the Easterling was used as a basis for
standardizing English coinage. As time went on, the name was shortened to
"Sterling"- which is still in use today, referring to the
English monetary system, and to a particular alloy of silver.

The word "sterling" represents the best known and most
respected quality marking in use today. It signifies that the article so
stamped is made from silver with a silver content of at least 92.5% by
weight, with no stipulation about the remaining 7.5%. The reason for the
relatively "low" silver content in sterling is a practical one:
finer grades of silver are too soft for everyday use. Alloying elements
are needed to increase strength and hardness. Since copper provides the
best combination of wear qualities, it is the most common alloying element
used by jewelers and silversmiths.

Although the legal minimum silver content for sterling is 92.5%, it is
significant to note that all Handy & Harman sterling silvers are
produced by starting with an alloy that has 92.7% silver. The extra
percentage of silver compensates for any minute loss of silver during
processing, and guarantees that all finished sterling will end up with at
least 92.5% silver content.

Molten silver and copper are completely soluble in each other in all
proportions. However, alloys which have copper contents ranging from about
2% through 27%, when solidified and examined under a microscope, exhibit
two discrete constituents: one is nearly 100% silver; the other is a
silver-copper "eutectic" (71.9% silver; 28.1% copper),
whose melting point is 1435ºF (780ºC.) (Note: In a two-metal alloy
system, the "eutectic" is a specific ratio of the two metals
that exhibits the lowest melting point.)

When standard sterling silver is cooled, microscopic analysis shows
both of the above constituents to be present in the solidified sterling.
The alloy is entirely liquid at 1640ºF (890ºC.) -and entirely solid at
1435ºF (780ºC.) However, the degree of copper solubility in the solid
alloy depends on the heat treatment used, and the overall physical
properties of the sterling can be materially affected, not only by heating
the silver to different temperatures, but also by employing different
cooling rates.

Silver alloys are normally supplied soft- for easy working. If desired,
the alloys can be supplied in various tempers, by reducing (working) the
alloy without annealing it.

Though virtually all sterling silvers consist of the same alloy of
copper and silver, their properties are greatly
affected by working and by heat treatment, such as annealing and
quenching.

In sterling and coin alloys, the copper tends to dissolve into the
silver, resulting in a homogeneous, large- structure, which is naturally
soft and ductile. Cold working these alloys-by rolling, pressing,
hammering or wire drawing-causes some of the crystals to become deformed
and smaller, which reduces the alloy's ductility.

Heat treatment can also be used to increase hardness (and decrease
ductility). The process, known as precipitation hardening, is described
below, and involves heating and cooling the silver in such a way as to
cause copper to precipitate out of solid solution, thereby producing a
fine- binary structure. This type of structure is hard, but it is also
difficult to work, and has a tendency to crack.

As mentioned, silver alloys can be supplied with custom tempers
(hardness), defined by the degree of cold-working performed. "Half
hard" describes a reduction of the cross- by two B & S gauges;
"hard" has been reduced by four B & S gauges, and
"spring hard" represents a reduction of 6-10 B & S gauges.

When a specific degree of hardness is desired in the finished article
of jewelry or silverware, it is best obtained by controlling the amount of
work done on the article after the final anneal, with all work being
performed uniformly over the entire piece to prevent cracking at
stress points.

Precipitation hardening involves the following procedure:

Heating the alloy to 1375-1400ºF (745-760ºC.)

Holding at temperature for 15 minutes.

Quenching rapidly in cold water.

The alloy is now in a softened condition, and can be re-hardened by
heating to 600ºF (316ºC.) for 30-50 minutes and then air cooling. The
resulting hardness is equivalent to the hardness obtained by cold working
to a 50% reduction.

Annealing is an effective method for re-softening silver alloys that
have lost their ductility due to working or heat treatment. It permits
sterling to be worked with reductions of 90% and even more. When the metal
becomes too hard for further working, it is simply annealed and
re-softened. Specific annealing procedures for sterling alloys should be
available from the supplier, and these recommendations should be followed
scrupulously, since even small differences in temperatures and/or cooling
rates could significantly affect the physical characteristics of the
alloy.

When sterling silver is annealed, care must be taken to avoid
"overheating"-a condition that increases hardness by promoting
undesirable grain growth and a significant loss of ductility.

In torch annealing, it is particularly important not only to see that
no part of the work is overheated, but also that all parts of the object
or article are brought to the full annealing temperature. Since sterling
silver anneals so rapidly, it is not necessary to hold it at the annealing
temperature for very long.

Obviously, the use of a closed furnace has certain advantages, since
the temperature of the object can be more precisely controlled-and the
heat can be absorbed more uniformly. However, the annealing time must be
established by trial and error for articles of different size and shape
-and for different size furnaces.

It
is always preferable to anneal silver- alloys in a neutral or reducingatmosphere,
in order to prevent the formation of copper oxides. In addition to using a
controlled atmosphere for annealing, the alloy can also be protected from
the air by coating it with Handy & Harman's Handy Flux. Any residues
can easily be removed by rinsing the article in hot water, after it has
cooled below a "cherry red" color.

When silver alloys are annealed in open air, copper oxides will form.
These oxides are of two types. The upper layer is cupric oxide, which has
a black color; beneath the layer of cupric oxide there may also be another
layer of oxide (cuprous oxide), which, because of its reddish color, is
called "fire"

The black surface layer of cupric oxide can be removed by dipping the
article in a "pickling solution"- a 5%-10% water solution of
sulphuric acid. The pickling action can be accelerated by heating the
solution.

After pickling, if a reddish layer is visible, it may be removed by
polishing, but if it does not polish out, it can usually be removed by
dipping the area in a cold, 50% solution of nitric acid. Since the nitric
acid bath removes silver very rapidly, the operator must remove the
article from the bath as soon as the fire is dissolved and rinse
immediately with water. Any cloudy residue should be polished off
immediately.

The best annealing temperature for normal softening of
sterling silver is between 1100ºF and 1200ºF (593ºC.-649ºC).
Temperatures above 1200ºF (649ºC.) tend to dissolve the copper-rich
phase, and, unless the cooling rate is rigidly controlled, maximum
softness will not be achieved. At temperatures above 1300ºF (704ºC.) the
article, if worked, will develop an "orange peel" surface. At
temperatures below 1100ºF (593ºC.), the time required to achieve the
desired results increases to a point where it becomes uneconomical.

By applying Handy Flux paste to a section of the article prior to
heating, the operator has an excellent visual aid for determining when the
article reaches the proper annealing temperature, since Handy Flux becomes
completely clear, like water, at 1100ºF (593ºC.).

After annealing, the article may be either air-cooled or quenched in
water.

Sterling silver can be cast with excellent results, using the same
techniques and precautions recommended for gold casting. The silver for
casting is provided in a grain form, which helps facilitate the speed and
uniformity of melting.

Because sterling contains pure silver as well as a silver-copper
eutectic, it must be heated to 1650ºF (899ºC.) to be completely molten.
Complete solidification does not occur until the sterling cools to 1435ºF
(779ºC.).